I. Field of the Invention
This invention is directed to a process for producing paper using water-insensitive starch fibers to replace all or part of the cellulosic or other pulp conventionally employed, and to the paper produced thereby. The invention also relates to a novel method for the production of certain specialty papers, as well as to methods for the incorporation of functional additives into paper during the production thereof and for binding fibers in non-woven webs.
II. Brief Description of the Prior Art
Various natural fibers (other than cellulose) as well as a variety of synthetic fibers have been employed in making paper, however, all these replacements have failed to provide a commercially acceptable substitute for cellulose due to their cost, poor bonding properties, chemical incompatibilities, difficulty in handling in papermaking systems, etc. While it has also been suggested to use starch fibers in various aspects of the papermaking process, commercial attempts to use such fibers have not resulted in any degree of success and paper is still being manufactured almost completely from wood-based cellulosic ingredients--the supply of which is being rapidly depleted.
It is apparent that the aqueous systems normally employed in the paper making operations require pulp fibers possessing sufficient water-insensitivity that they can be used in all aspects of the manufacturing process throughout a relatively wide pH range without losing their integrity. In this regard, the few references which suggest the replacement of starch fibers for cellulose fibers (e.g. U.S. Pat. No. 1,682,293) require chemical modification of the starch in order to radically change its naturally occurring properties prior to forming the fiber so as to provide the degree of water-insensitivity required in the papermaking process. Alternatively, other references (e.g., U.S. Pat. No. 2,570,449) require that the papermaking process itself be modified as by replacing the conventionally employed aqueous system with an alcohol solvent in which the starch fibers are not soluble. It will be recognized that the use of such techniques is both impractical and uneconomical when employed on a commercial basis.
As another aspect of the papermaking operation, it is often necessary to incorporate additives into the pulp in order to achieve specific end properties. Thus, additives such as pigments, latices, synthetic microspheres, fire retardants, dyes, perfumes, etc. are often employed in the manufacture of paper. The efficient retention of these additives at the wet end of a paper machine presents difficulty to the manufacturer since that portion which is not retained creates not only an economic loss, but also a significant pollution problem if it becomes part of the plant effluent. Furthermore, such additives are also added via coating or saturation processes commonly known in the art. These processes usually require that excess heating energy be consumed to re-dry the paper after coating. Moreover, in some instances the coating systems are required to be solvent based which then creates extreme capital expense and requires regulation to recover volatile materials.
It is therefore an object of the present invention to provide a commercially viable process for the use of starch fibers as a partial or complete replacement for cellulose in conventional papermaking operations.
It is also an object to provide a process which efficiently enables the retention and incorporation of additives into paper during the manufacture thereof.
It is a further object to provide a process which enables water-insoluble additives to be introduced into the paper as fiber encapsulated additives.
Another object is to provide ordinary and improved specialty papers according to such process.
A further object of the invention is to provide an efficient and economical process for binding synthetic and/or natural fibers in non-woven web form.
These and other related objects will be apparent from the description which follows.